The present invention relates to an ultrasonic metering device with externally located ultrasonic transmitter-receivers. This device is structured so that it can be mounted on a pipe in which a fluid to be measured flows without altering the pipe and can be installed with a high accuracy.
Examples of an ultrasonic metering device of this general type are a flow meter, a densitometer and a current meter.
In mounting the ultrasonic metering device on a pipe, the following requirements should be satisfied:
(1) It is essential that the ultrasonic transmitter-receivers (hereinafter referred to as "ultrasonic transducers" when applicable) be correctly positioned relative to the pipe and relative to each other because the incident angle of the ultrasonic waves with respect to the fluid and the distance between the ultrasonic transducers greatly affect the accuracy of measurement.
(2) It is necessary that the ultrasonic transducers be sufficiently acoustically coupled to the pipe. Excellent sensitivity and accuracy cannot be obtained without satisfying this requirement.
(3) It is desirable that the ultrasonic transducers can be readily mounted on the pipe within a short period of time. One of the merits of the external mounting system resides in that the ultrasonic metering device can be freely mounted on pipes already installed in a plant.
Depending on the fluid carried by the pipe, the area around the pipe may not be suitable for the physical presence of workers such as due to the pipe being at high temperature, filled with poisonous gas or radioactive material. Thus, it is often required that the device can be readily and quickly mounted on a pipe even by unskilled persons without a need for adjustment.
However, no ultrasonic metering device satisfying all these requirements has yet been proposed in the art.